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The binding energy between hydrogen (H) and defects in solid phase materials has been widely studied, which is of vital importance to understand the H retention effects and defect growth mechanisms. However, present studies of binding energy through density functional theory (DFT) or the molecular statics (MS) method were usually performed at 0 K, which could not take the influence of entropy into consideration. In this work, a thermodynamic method has been proposed to obtain the trapping energy between H and defects at finite temperatures. The method is based on the rate theory, which uses trapping energy (V) and trapping range (δ) to describe the trapping properties of defects. Ultimately, a parameterized H spatial cumulative distribution function at thermodynamic equilibrium state could be given. The trapping energy and trapping range parameters in the function can be determined by contrast with the results obtained from molecular dynamics or other methods. This method has been applied to calculate the trapping energies and trapping ranges of H to helium bubble and grain boundary, respectively. Further discussion has been made on the discrepancy between trapping energies obtained by this method and the conventional DFT/MS method. [ABSTRACT FROM AUTHOR]

Low-energy ion beam irradiation, combined with the introduction of impurities, presents a promising approach for nanopatterning silicon (Si) surfaces. In this research, we investigate the surface evolution of Si (100) surfaces irradiated by 75 eV helium (He) plasma, in the presence of tantalum (Ta), traditionally regarded as an impurity incapable of initiating pattern formation, as evidenced in prior studies. The Ta impurities are pre-deposited onto the Si surfaces using the magnetron sputtering method, which offers a more controlled and quantifiable approach compared with the conventional co-deposition route. After irradiation at 800 K, dense cone arrays are produced on the Si surface. The growth of the cones is explored for fluence spanning (1–10) × 1025 m−2. The cross-sectional scanning electron microscope images indicate that the cone lengths and base width are well characterized by t1/2 dependence. The kinetics of the cone growth follow Fick's law, characterized by an effective diffusive mechanism with the coefficients of diffusion: D = 6.49 ± 0.83 × 10−16 m−2 s−1. Transmission electron microscope observations reveal that the cone has distinct inner and outer parts with different microstructures and a clear interface. The growth mechanism of these cones is elucidated as a composite process involving preferential sputtering, the destabilizing influence of He bubbles, and the migration of adatoms. [ABSTRACT FROM AUTHOR]

BackgroundFusion reactor engineering models are extremely complex, which makes the modeling of the neutronics analysis rather tedious and time consuming. The open-source Monte Carlo code OpenMC can directly perform particle transport simulation on CAD models by integrating DAGMC (Direct Accelerated Geometry Monte Carlo), which can significantly improve the modeling and analysis efficiency of complex engineering models.PurposeThis study aims to carry out the application research of OpenMC in fusion neutronics analysis for China Fusion Engineering Test Reactor (CFETR).MethodsBased on the CFETR 1D cylindrical shell model, the consistency of tallies of OpenMC and MCNP was verified. According to the characteristics of plasma spatial distribution, source class and source function were customized on base of the source extension interface to accurately describe the complex fusion neutron source. The 3D model of complex CFETR engineering was successfully established by using CAD geometry function of DAG-OpenMC, and the neutron wall load distribution, tritium breeding ratio (TBR) and heat were obtained.ResultsThe calculation results of DAG-OpenMC and MCNP have excellent consistency. The neutron wall load peak of CFETR appears at the mid plane, and the tritium breeding ratio of helium cooled ceramic breeder blanket is 1.141. When the fusion neutron power is 160 MW, the total nuclear heat generated is 211.73 MW, and the global energy multiplication factor is 1.32, in which the total nuclear heat generated by the blanket is 185.64 MW, accounting for 87.68% of the total nuclear heat.ConclusionsThe CAD-based geometry capabilities greatly improve the modeling efficiency of building complex fusion reactor engineering models. Verification of the key issues of DAG-OpenMC in fusion neutronics applications by this study, indicates its feasibility in dealing with fusion neutronics problems under complex engineering structural conditions.

The heat flux width (λq) is a key parameter determining the heat load at divertor targets. In recent years, drifts have been found to play a remarkable role in the edge plasma transport, while its influence on λq has not been well understood. Investigations of the influence of drifts on λq, systematic simulations using the SOLPS-ITER code are performed in this work. The statistics of the simulation results show that the drift under favorable/unfavorable B T tends to increase the λq in the outer/inner side and decrease the λq in the other side, which is consistent with the experiment observations. At the upstream and the target, the mechanisms of the influence of the drifts on λq are different. The upstream λq (λq,u) is directly affected by the drift-induced convective heat flux, while λq at the target (λq,t) is indirectly influenced through heat conduction (in the high-recycling regime) and the sheath (in the detached regime) due to the change of plasma parameters there. Furthermore, the synergetic effect of geometry and drift under favorable B T leads to an anomalously large λq,t in the inner side at high density. [ABSTRACT FROM AUTHOR]

Edge localized modes resulted from magnetohydrodynamic (MHD) instabilities in the pedestal region are a significant concern for future tokamaks. In this work, Ci‐Liu‐Ti (CLT), an MHD code in the three‐dimensional toroidal geometry, is applied for the linear simulation of the ideal pedestal MHD instabilities. The simulations are performed for the experimental advanced superconducting tokamak‐like elongated divertor configuration with large triangularity, which is generated by the high‐accuracy free‐boundary equilibrium solver (CLT‐EQuilibrium, i.e., CLT‐EQ) developed recently. The present work focuses on the influence of the magnetic shear, which is scanned by adjusting the pedestal current with a fixed pedestal pressure profile. As the pedestal current increases, both the local (Slocal) and global (Sglobal) magnetic shear decrease. The ballooning mode is destabilized along with the decrease of Slocal, and stabilized when Slocal is negative for the whole region of bad curvature, which implies the access of the second stable region. Further increase of the pedestal current leads to the destabilization of the kink mode, which is stabilized again until Sglobal is negative at the location of significant gradient of current density. The simulated results are consistent with the findings in Radovanovic et al. Nucl. Fusion 62 (2022) 086004 and C. K. Sun et al. Phys. Plasmas 25 (2018) 082106, which indicates the availability of CLT in the linear simulation of the ideal pedestal instabilities. [ABSTRACT FROM AUTHOR]

Background: The optimal treatment approach for low‐risk prostate cancer (LRPC) remains controversial. While active surveillance is an increasingly popular option, definitive local treatments, including radical prostatectomy (RP), external beam radiotherapy (EBRT), and prostate seed implantation (PSI), are also commonly used. This study aimed to evaluate the survival outcomes of patients with LRPC using a large patient population from the National Cancer Database (NCDB). Methods: We analyzed data from 195,452 patients diagnosed with LRPC between 2004 and 2015 using the NCDB. Patients were classified based on their treatment modalities, including RP, EBRT, PSI, or no local treatment (NLT). Only patients with Charlson–Deyo comorbidity scores of 0 or 1 were included to ensure comparability. Propensity score analysis was used to balance the treatment groups, and the accelerated failure time model was used to analyze the survival rates of the treatment groups. Results: After a median follow‐up of 70.8 months, 24,545 deaths occurred, resulting in an all‐cause mortality rate of 13%. RP demonstrated a survival benefit compared with NLT, particularly in patients younger than 74 years of age. In contrast, radiation treatments (EBRT and PSI) did not improve survival in the younger age groups, except for patients older than 70 years for EBRT and older than 65 years for PSI. Notably, EBRT in patients younger than 65 years was associated with inferior outcomes. Conclusion: This study highlights the differences in survival outcomes among LRPC treatment modalities. RP was associated with improved survival compared to NLT, especially in younger patients. In contrast, EBRT and PSI showed survival benefits primarily in the older age groups. NLT is a reasonable choice, particularly in younger patients when RP is not chosen. These findings emphasize the importance of individualized treatment decisions for LRPC management. [ABSTRACT FROM AUTHOR]

Tungsten (W) impurity eroded from the divertor target can degrade the confinement performance of future fusion reactors. The mechanism of the effect of E × B drift on the W transport in the scrape‐off layer (SOL) was investigated with a fixed cross‐field anomalous particle diffusion coefficient for W ions (D⊥,W) of 1 m2s−1 in our previous simulation work, which indicates that the W flux entering the confined region (Γenter) and mean W concentration in the confined region (CWavg$$ {C}_{\mathrm{W}}^{\mathrm{avg}} $$) can be increased by more than one order of magnitude by drifts. In this work, the influence of the cross‐field anomalous diffusion on the W transport in the SOL is further investigated. The basic flow pattern of the W ion flux (ΓW) keeps when D⊥,W varying from 0.5 to 3 m2s−1, and Γenter mainly comes from the hotter divertor region. Results show that D⊥,W value affects the W leakage from divertor region and entry into confined region. Therefore, Γenter and CWavg$$ {C}_{\mathrm{W}}^{\mathrm{avg}} $$ both decrease with increasing D⊥,W. Mechanisms for cases w/wo drifts are compared. [ABSTRACT FROM AUTHOR]

Background: Urachal carcinoma (UrC) is a rare, aggressive cancer with a poor prognosis that is frequently diagnosed in advanced stages. Due to its rarity, the current staging systems, namely Sheldon, Mayo, and Ontario were established based on relatively small patient cohorts, necessitating further validation. We used a large patient population from the National Cancer Database to model a novel staging system based on the Tumor (T), Node(N), and Metastasis (M) (TNM) staging system and compared it to established staging systems. Methods: We identified patients diagnosed with UrC between the years of 2004–2016. To determine median overall survival (OS), a Kaplan–Meier (KM) curve was generated using the Sheldon, Mayo, Ontario, and TNM staging system. A cox proportional‐hazards regression model was developed to highlight predictors of overall survival. Results: A total of 626 patients were included in the analysis. The OS for the entire cohort was 58.2 months (50.1–67.8) with survival rates at 12, 24, and 60 months of 83%, 70%, and 49%, respectively (p < 0.0001). As compared to the Sheldon, Mayo, and Ontario staging system, our TNM staging system had a more balanced sample and survival distribution per stage and no overlap among stages on KM survival curves. The Mayo, Ontario, and TNM staging systems were more accurate in terms of stage‐survival correlation than the Sheldon staging system (p < 0.05 for all stages). Conclusions: The proposed novel TNM staging system for UrC has a more balanced sample distribution and a more accurate stage‐survival correlation than the traditional Mayo, Sheldon, and Ontario staging systems. It is clinically applicable and enables better risk stratification, prognosis, and therapeutic decision‐making. [ABSTRACT FROM AUTHOR]